The use of sandwich rubber to cover surfaces which are exposed to abrasion by heavy goods is increasing. A sandwich material known in the art comprises two different rubber qualities, one with a hardness of 60.degree. Shore A and another with a hardness of 40.degree. Shore A. This composite material is considerably superior to homogenous materials, as the harder rubber layer resists the hard and sharp edges of the goods, while the softer layer is considerably more resilient and therefore may yield. This provides for a considerable reduction of damage due to crushing and fatigue, while at the same time the thickness of the material may be reduced. In spite of these considerable advantages of the existing sandwich rubber material there is a strive for better materials to satisfy the demands of the market for greater impact resistance and consequent increased working life and/or lower weight and other positive properties.
Another known technique is to coat rubber with a thin layer of polyethylene in order to combine the low friction of the polyethylene with the ability of the rubber to absorb shocks and blows. This material has been used inter alia as a supporting material under conveyor belts at the loading point. One drawback of the material is that it must be comparatively thick, and consequently becomes heavy and occupies valuable space. Further, the polyethylene layer has proven to expand as a result of blows, in the end leading to a separation of the polyethylene layer from the rubber layers. This is a serious drawback. In addition, polyethylene has a low resistance to abrasion, which may result in a quick scuffing of the surface layer. This is especially serious because it is virtually impossible to renew the polyethylene layer by spraying on a new one or elsewise equally simple, the complete replacement of the entire material being required instead.